Article comprising porous rubber



Aug. 25, 1942.

C. L. BEAL ARTICLE COMPRISING POROUS RUBBER Original Filed Aug. 12, 1938 mil [H1 Patented Aug. 25, 1942 2293.928 ARTICLE comrarsnrc ronous RUBBER Carl L. Bea], Cuyahoga Falls, Ohio, assignor to American Anode Inc., Akron, Ohio, a corporation of Delaware Original application August 12, 1938, Serial No.

Divided and this application December 31, 1940, Serial No. 372,472

9 Claims.

ing application Serial No. 224,486, filed August According to the present invention, such porous articles and surfaces are, produced by'treating a base member with a latex-coagulating composition containing an acidic material such as acetic acid and associating the treated base member with a rubber latex composition containing an agent such as ammonium carbonate which will react with the acidic material to evolve considerable quantities of gaseous material at the interface between the base member and the latex as well as within the forming layer of latex coagulum as thelatex is progressively coagulated by the coagulating composition. In this manwhich is pervaded by a multitude of pores in the form of irregular craters originating adjacent the face of the layer in contact with the base member and increasing in cross-sectional area out-,- ward to the other face of thelayer. Such pores frequently are of microscopic dimensions-at one face and increase irregularly to microscopic dimensions of the order of ,4 .to 34 inch in average diameter at the other face. Such porous rubber sheets make unusually satisfactory filter cloths when used with the finely porous face as the filtering surface as the crater shaped pores will not clog as do pores of substantially uniform size from face to face. Such sheetsalso function satisfactorily as electrolytic diaphragms and may be used as separator plates in storage batteries. In a modified embodiment of the invention, it has been found that. such a porous rubber layer may advantageously be produced as a thin exterior coating upon an imperforate rubber article to provide a non-slip and decorative surface, the finely porous inner face merging with the body ner, there is produced a rubber layer or sheet 355 of the article proper after vulcanization to provide a strong mutual bond while the coarsely porzf ous. outer face provides an unusually efficient nonslip surface which may include variegated colors to produce decorative effects. A I

The invention will be described more fully with reference to the accompanying drawingof which Fig. l is a sectional elevation illustrating an early step in manufacturing a filter cloth according to the present invention and showing a basemember being treated with an acidic composition which will coagulate rubber latex; I

Fig. 2 is a sectional elevation illustrating a succeed ing step in the process and showing the acidtreated base member associated with a liquid rubber latex composition receiving a coating deposit of rubber;

Fig. 3 is a sectional elevation illustrating the steps of drying and vulcanizing the rubber;

Fig. 4. is a. fragmentary sectional perspective view on a considerably enlarged scale showing a filter cloth made according to the present invention;

Fig. 5 is a vertically sectioned fragmentary perspective view showing an electrolytic diaphragm embodying the principles of the present invention, the pores in the diaphragm being arbitrarily shown considerably enlarged for clarity of illustration;

Fig. 6 is a sectional elevation illustrating an early step in manufacturing an article such as a rubber glove having a non-slip surface, and showing a glove deposition form immersed in liquid rubber latex composition for receiving a coating deposit of latex coagulum;

Fig. '7 is a sectional elevation illustrating a succeeding step in the manufacture of the glove and showing the coating deposit of rubber coagulum being treated with an acidic composition;

.Fig. 8 is a sectional elevation illustrating a latex step in the manufacture of the glove and. showing the acid-treated. deposit of latex coagulum associated with a latex rubber composition containing a gas-producing agent;

- Fig. 9 is an elevation of a finished glove having a rough non-slip surface produced according to the present invention; and

Fig. 10 is an enlarged fragmentary sectional perspective view showing a portion of the glove of Fig. 9, and illustrating in a general way the character of'rough porous surface produced in the present invention.

The base-members utilized in the present process preferably are porous or bibulous in character for the purpose of absorbing and retaining substantial quantities of acidic material for subsequent reaction-with the gas-producing agent in the latex, although impervious base members often may be employed with complete satisfaction, especially when very thin layers of porous rubber are to be produced:

-To produce a filter cloth, for example, the base member may be an unglazed porcelain or other the process, the

porous ceramic plate base member an acidic composition H such as a 20% aqueous solution of acetic acid, as by momentarily immersing the base member in the acidic composition as shown in Fig. 1 to permit the porous base member to absorb a considerable quantity of the acid composition. The treated base member then is associated with and preferably is immersed in (Fig. 2) a liquid rubber latex composition l2 containing, for example, 2% by volume of ammonium carbonate together with the usual vulcanizlng, compounding and conditioning ingredients. The base member is permitted to remain in the latex for about three minutes and then is withdrawn after which the base member is found to ill of appropriate size. In

I!) is-treated with be enveloped by a substantially uniform layer of porous coagulated rubber l3 about inch thick. To prevent the formation of an impervious skin on the outer face of the layer as a result of subsequent drying of uncoagulated latex remaining on the surface, the rubber layer is promptly washed with an alkaline solution preferably containing a colloidal material. An aqueous solution containing 1 part by volume of concentrated (28%) ammonium hydroxide in 100 parts of dis tilled water, or an equivalent quantity of sodium hydroxide or potassium hydroxide, together with from 0.2% to 1.0% of a colloid such as gelatine, casein, gum arabic, agar, soap, etc. is quite satisfactory for this purpose, The porous layer next is washed in rlmning water for several hours to leach out water-soluble materials and then is dried and vulcanized in any conventional manner as by heating for an appropriate time in a hot air oven ll as shown diagrammatically in :Fig. 3. If a freely flexible cloth is desired, the latex composition may be compounded and vulcanized to produce a soft-vulcanized rubber sheet. In other cases where decreased flexibility is not undesirable,- the rubber may be compounded and vulcanized to produce a hard-vulcanized porous rubber sheet which will be especially useful for filtering many corrosiv solutions to which hard rubber is more resistant than other materials. The porous rubber may be vulcanized while still on the base member as illustrated in Fig. 3, or the unvulcanized deposit may be removed from the base member and thereafter vulcanized In either case, the envelope preferably is slit along the edges, either before or after vulcanization,- to provide two similar sheets of porous rubber which may be used as filter cloths. If desired, such a porous rubber sheet l3a may be provided with a reenforcing element, as' by cementing a coarsely woven sheet of textile fabric l5 to one face, preferably the finely porous face, of the rubber sheet to producea finished filter cloth as illustrated in Fig. 4. Such a filter cloth will be used, of course, with the fabric-reenforced finely porous face as the filtering surface, buthas been illustrated in Fig. 4 with the coarsely porous faceup in order to show the character of the pores more clearly.

As illustrated in Figgi, the pores in a porous rubber sheet made according to the present invention are crater-like in form and usually extend from one face of the sheet to the other face with gradually, but not uniformly, increasing cross-sectional size. As has been indicated, the poresfrequently areof microscopic dimensions at the finely porous face and increase to macroscopic dimensions of the order of /64 to /1s inch average diameter at the coarsely porous face.

As may readily be appreciated, any material surfaces having face to face.

In many cases, the base member may be. permitted to remain associated with the porous rubber layer to become an integral part of the finished product. For example, the invention may be used to produce electrolytic diaphragms in which case the base member may be textile fabric, porous paper, or similar porous sheet material. A microporous paper sheet is especially satisfactory for this p se as the microporous paper not only provides reenforcement for the necessarily rather fragile rubber deposit but also provides a microporous screen across any pores in the rubber sheet which may be undesirably large at the finely porous face.

Such an electrolytic diaphragm illustrated in Fig. 5 ordinarily will consist of a microporous sheet of rather heavy paper or other fibrous material 2| of appropriate size completely enveloped by an adherent porous rubber layer 22 produced according to the present invention by treating the fibrous sheet with an acid composition and associating the treated sheet with latex containing a gas-producing agent substantially as hereinabove described. In such a diaphragm, the pores will be substantiallymicroscopic in dimensions adjacent the fibrous insert and will increase in size outwardly to macroscopic dimensions at the exposed faces of the rubber. The porous rubber of electrolytic diaphragms usually will be vulcanized to the hard rubber state.

The invention also is useful in providing rough non-slip and/or decorative characteristics upon many types of articles where such surfaces are of value. For example, socalled household rubber gloves advantageously may be provided with a rough non-slip surface to prevent slippage when the wearer is handling wet or moist articles such as wet dishes.

To manufacture a rough-surfaced rubber glove according to the present invention, (Figs. -6 to 10) a conventional glove form 3| is immersed in a standard compounded rubber latex composition 32 and a coating of latex rubber 33 about 0.010 inch thick (when dried) i deposited upon the glove form in any well-known manner. The glove form 3| together with the undried deposited rubber coating 33 then is treated with an acidic material, as by immersing the form and deposit in a 25% aqueous solution of formic acid 34 and a considerable quantity of the-formic acid solution is permitted to soak into the undried latex rubber .layer. The treated rubber layer then is immersed in a compounded latex composition 35 containing 2% by volume of ammonium carbonate together with the usual compounding, conditioning and vulcanizing agents required to produce a high grade soft-vulcanized rubber vulcanizate. The treated form is permitted to remain in the latex 35 for one minute and then is withdrawn, washed, dried, vulcanized and stripped from the form in the usual manner.

The finished household glove illustrated in Fig. 9 is found to have a rough porous surface layer 36 providing an unusually effective non-slip surface integ'rally bonded by the concurrent vulcanthe main imperforate body of the glove is therefore substantially continuous and permits a layer are much larger and present. a veined, pitted surface having unusual non-slip characteristics.

Colored latices may be used in producing the porous surface layers in which case pleasing decorative effects will be obtained, particularly if the porous layer is quite thin and of a color differing from the color of the imperforate body of the glove. Effects of the latter character are beneficial in toy balloons as the infiation of the balloon stretches the colored porous layer to a lacy colored net work contrasting with the differently colored body of the balloon which shows through the lacy layer in spots.

In such cases where only a very thin porous layer is required and the coagulating effect of the acidic treating, material on the latex is not needed to build up a heavier layer, the latex composition containing the gas-producing agent may be applied directly to an untreated base member and the layer of latex then treated on the exposed surface with acidic material to produce the porosity.' Such procedure will, however, produce a porous deposit of somewhat different character and appearance as the gas is not evolved at the interface between the base member and the latex nor during formation of the deposit'as in the preferred procedure.

Numerous modifications in details of the invention as hereinabove described of course are possible. The deposition base may be made of any conventional material but, as has been indicated, desirably should be sufficiently porous or bibulous to absorb a substantial quantity of the acidictreating material. Spongy rubber, porous ceramic ware, wood, bibulous paper, fabric and the like may be used as the deposition base member. If very thick porous coatings are desired the porous-layer producing steps of the process may be repeated several times, each porous layer serving as a base member for absorbing acid to produce the succeeding porous layer. Organic solvents such as alcohol, acetone, or the like may be used as the solvent for the acid instead of water as described, and other organic or inorganic acids such as propionic, dilute hydrochloric or dilute sulfuric, etc. may replace the formic andacetic acids specifically mentioned. Likewise, the acid solution may contain other latex coagulants such as bivalent metallic salts to assist in co ulating the porous latex layer, and in many cases will contain a well known wetting agent to promote uniform interfacial natural or synthetic rubber and rubber-like materials and may contain any desirable thickening,

thinning, preserving, stabilizing, compounding, vulcanizing, age-resisting or other conditioning agents, according to conventional practice. The term latex rubber similarly refers to rubber deposited in situ directly from such liquid rubber latex.

All. such modifications and variations are within the scope of the invention as defined by the appended claims.

I claim:

1. A body of latex rubber pervaded by a multitude of crater-shaped pores, the individual pores varying irregularly in dimensions from microscopic openings at one face of the body to macro-' scopic openings at an opposed face of the body.

2. An article of manufacture including a body of latex rubber pervaded by a multiude of cratershaped pores extending substantially from face to face of the body, said pores being very fine at one face of the body and increasing irregularly in size to relatively coarse openings at the other face, the coarse openings providing a rough surface having non-slip characteristics.

3. An article of manufacture comprising a base member and adhered thereto a layer of latex rubber pervaded by a multitude of crater-shaped pores, the individual pores varying irregularly in dimensions from relatively small dimensions in a zone contiguous to the base member to relatively large dimensions in a zone removed from the base member.

4. An articleof manufacture comprising a base member of imperforate rubber having integrally attached to a surface thereof a coating layer of latex rubber pervaded by a multitude of cratershaped pores, the individual ores being relatively small in a zone contiguous to the imperforate rubber base member and permitting a strong vulcanized bond between the two layers but increasing to relatively large openings. in the opposite face of the porous layer to provide a discontinuous, rough surface at the exposed face of the layer.

.5. A'rubber glove comprising an imperforate glove body having integrally attached to at least a portion of its exposed surface a coating layer of porous latex rubber providing a rough, non slip surface.

6. A vulcanized rubber article comprising a shaped body of imperforate rubber having integrally attached to at least a portion ofits exposed surface a coating layer of porous latex rubber providing a rough surface.

7. An article of manufacture comprising a porous base member of sheet material having adhered thereto a coating layer of latex rubber pervaded by a multiude of crater-shaped pores.

8. A non-clogging filter cloth comprising a sheet of latex rubber pervaded by a multitude of similarly disposed crater-shapedpores extending from face to face of the sheet.

9. An electrolytic diaphragm comprising a porous base member coated with a layer of latex rubber pervaded by a multipde of crater-shaped pores.

CARL L. BEAL. 

